Bollgard sequel outperforms original

Second protein improves efficacy and spectrum of pest control Two years of university tests indicate that Bollgard II, the sequel, might be an even bigger hit than Bollgard, the original.

Bollgard II cotton, which is expected to have EPA approval in late 2001, contains the Bt protein Cry1 Ac, the same protein in original Bollgard cotton. Plus, it has a second protein, Cry2 Ab, which was added in hopes of improving Bt cotton's efficacy and spectrum of control.

According to laboratory and field tests conducted by Mississippi State University entomologist Scott Stewart and others, Bollgard II provided the same high level of tobacco budworm control as Bollgard.

In addition, the tests showed increased control of cotton bollworm and good-to-excellent control of other lepidopteran pests. "Relative to Bollgard cotton, Bollgard II clearly delivers a higher dose of toxin to all the lepidopteran species in the studies," Stewart said. "Bollgard II is really good on the less-common caterpillars like beet armyworm, soybean looper and fall armyworm."

Stewart presented the data at the Cotton Incorporated Crop Management Seminar in Memphis.

"We still have one to two years of testing before we hit the market," Stewart said. "Next year, there's going to be some testing with other varieties. I'd like to evaluate Bollgard II on those varieties, too, to make sure there aren't any little glitches or hangups."

Unexpected problems did arise with Bt cotton containing Bollgard after it was adopted commercially and planted on millions of acres in the mid- to late-1990s. Growers found that cotton bollworms frequently reached treatment levels in Bt cotton, a problem related to lower concentrations of the Bt protein in parts of the plant that are not green in color, like flowers.

It's too early to tell if that's going to happen with Bollgard II cotton. Tests on how the Bt protein is distributed in Bollgard II are not complete. However, Stewart noted, "If the technology continues to perform like it has in the tests I've seen, it would be very unlikely that growers would have to overspray for bollworms. But we still have some testing to do."

Bollgard technology and boll weevil eradication promise to virtually eliminate most lepidopteran pests and the boll weevil as serious problems in many parts of the southern Cotton Belt, which could add a new term to our vocabulary, "low spray environment."

In such an environment, which seemed almost inconceivable six or seven years ago, a new spectrum of pests will likely come into play, according to Stewart.

"Rare, oddball or occasional pests are going to become a little more prevalent. Depending on temperatures and conditions, we're going to be dealing more with stinkbugs. We're going to have just as much of a problem with plant bugs."

Stewart stresses that even resistant plant bugs are an improvement over the resistant tobacco budworms that attacked cotton crops of the early- to mid-1990s, "requiring $12 applications going out at five-day intervals, plus making five to six shots for weevils."

On the other hand, a low spray environment "actually makes the scouting job tougher because we'll be looking for pests that may be a little harder to detect. It's going to be harder to predict what kind of damage they're going to cause."

Monsanto, which holds the rights to Bollgard and Bollgard II, has said that both products will be on the market together for a short period of time, but that Bollgard II eventually would replace Bollgard in Bt cotton varieties. Monsanto has not released any information about the cost of Bollgard II.

For some growers, the value of Bollgard II will not be any greater than it was for Bollgard, according to Stewart. "It will depend in large part on where you are. In places like the Bootheel of Missouri, that may never have beet armyworm and fall armyworm and loopers, Bollgard II probably won't be that much of an improvement over Bollgard. In places that deal with heavy bollworm pre sure and sporadic other pests, it's going to have some increased value."

Studies by MSU also indicated that there were no significant yield differences between the varieties included in the tests - DPL50, a conventional variety, DPL50 B, which contains Bollgard, and DPL 50BII, which contains Bollgard II, when the plots were treated as needed for lepidopteran pests as needed.

In field plots of Bollgard and Bollgard II cotton at Stoneville in 2000, Bollgard II reduced populations of bollworm larvae by 86 percent, compared to 57 percent for Bollgard. Percent control of tobacco budworm, at 99.9 percent, was the same for Bollgard and Bollgard II.

In addition, the tests indicated that Bollgard II: reduced the percentage of loopers in the field tests by 99 percent, compared to zero percent for Bollgard; reduced fall armyworm by 87 percent compared to 20 percent for Bollgard; reduced beet armyworm by 86 percent, compared to 30 percent for Bollgard; and reduced saltmarsh caterpillar by 97 percent, compared to 29 percent for Bollgard.